The inductorium: the stimulator associated with discovery

The inductorium, or induction-coil stimulator, introduced in the late 1830s, provided a means for obtaining repetitive stimuli; thereby allowing the discovery of new properties of excitable tissues. Major physiologic discoveries with the inductorium were tetanic contraction of skeletal muscle, inhibition of the heart, the role of vasomotor nerves, and cortical localization. In the hands of clinicians, it was used to diagnose neuromuscular disease and to produce artificial respiration with body-surface electrodes. Because of the historical importance of this tool, its characteristics are described quantitatively. Although it is no longer used, it has a secure place in the history of biomedical instrumentation.